1. Technical Field
The present invention relates to a data processing applicable to the display devices, such as the television sets and the monitors, as well as the image processing devices for creating the images of the computer graphics, more particularly to a color correction processing circuit designed to be capable of correcting the colors of the image data based on the 3 colors, i.e., the red color, the green color and the blue color, in consideration of the difference in the system of various image processing devices.
2. Background Art
Conventionally, in displaying the color according to the inputted color signal on a display device such as a monitor screen, it has been a common practice to adjust the color tone depending on the operating conditions of the display devices so that the image having the desired color can be reproduced. The color tone adjusting process can be divided broadly into the 2 processes, namely the table conversion process and the matrix operation process.
According to the table conversion process, the image data corresponding to the red color, the green color and the blue color (hereinafter referred to as R, G and B respectively) are inputted so that the optimal image data selected out of the image data for R, G and B, which have undergone the color tone adjustment process and stored in the memory such as a ROM or the like, can be outputted responding to the inputted image data; the table conversion method permits to adopt any color tone adjusting characteristic and thus is advantageous in realizing the color tone adjustment for good color reproduction. This conventional process, however, has a problem such that the process, which is designed simply for storing the data for each combination of the image data, requires a memory of a large capacity as large as about 400 M bits, and the similar problems still occurs even when the memory capacity is compressed to a certain extent; thus, it is difficult to permit the application of the LSI to such a process, and such process has another problem that the system of the process is not sufficiently elastic to the alteration of the operating conditions or the like.
In contrast, the color tone adjusting process employing the matrix operation method is designed so that the color tone adjusting values (amounts) to be outputted are calculated directly on the bases of the luminance signals and the color difference signals, Y, Cr and Cb, converted from the inputted R, G and B signals, or the originally inputted R, G and B signals. For instance, there is an operation method for obtaining the output signals, R′, G′ and B′, by multiplying the inputted R, G and B signals by the matrix coefficients arranged in 3 rows and 3 columns. This operation formula can be expressed as given hereunder.
                              [                                                                      R                  ′                                                                                                      G                  ′                                                                                                      B                  ′                                                              ]                =                              [                                                                                a                    11                                                                                        a                    12                                                                                        a                    13                                                                                                                    a                    21                                                                                        a                    22                                                                                        a                    23                                                                                                                    a                    31                                                                                        a                    32                                                                                        a                    33                                                                        ]                    ·                      [                                                            R                                                                              G                                                                              B                                                      ]                                              (        1        )            
This color tone adjusting process by using the matrix operation method does not require the large-capacity memory, which has been discussed previously in connection with the table conversion process, and thus permits the application of the LSI. Further, (the color tone adjusting process) can be adapted flexibly to the alteration of the operating conditions by properly adjusting each of the elements a11-a33 of the coefficients of the matrix given in the above equation (1). As the color tone adjusting process by using the matrix operation method, there are the following references, i.e., the Reference 1 or the Reference 2.
Patent Reference 1: Laid-Open Patent Application No.2003-111091
Patent Reference 2: Laid-Open Patent Application No.2001-223911
In the conventional color tone adjusting process by using the matrix operation method, the hue made available by the combination of the inputted R, G and B signals is determined to calculate the amount of adjustment required for the hue to be adjusted. For instance, as shown in FIG. 3, (in the case of the conventional color correction process,) the given color is divided into the 6 color ranges, namely the red range, the green range, the cyan range, the blue range, the magenta range, for the fine correction of the colors; however, such a conventional color correction method is not good enough because of that the peripheral area of each color range is left almost uncorrected as being uncorrectable range.
Besides, there have been the conventional circuit designed for the color tone adjustment and the white balance adjustment in parallel; however, in the case of such a conventional color tone adjustment circuit, the white balance adjustment is made by adjusting the gains of the R, G and B, and it is known that using such a conventional circuit for the white balance adjustment results in the deterioration of other colors. Further, both in the case of the previously mentioned color correction process and in the case of the white balance adjustment process, the final adjustment has to be made by the user who is supposed to determine the degree of the necessary corrections while watching the condition of the image on the display screen; however; such conventional circuit is not designed to permit each user to make necessary adjustment while observing the condition of the image displayed on the screen before adjustment, so that the user is unable to make the fine settings for adjustment.
The present invention is proposed for resolving such problem of the conventional color correction process by providing a color correction processing circuit for each hue designed not only for enabling the user to make appropriate color correction for each of the hues in any given image without leaving any uncorrected ranges but also for enabling the white balance adjustment to be made without sacrificing other colors, as well as for enabling the user to make desired color correction by each hue while watching the condition of the image before correction.